PECTORAL AND DELTOID REGION. 101 



sternal origin, the pectoralis major is perforated by a num- 

 ber of arterial twigs which come from the internal mam- 

 mary artery, and, piercing the intercostal spaces, supply 

 the muscle and the integument. 



The mammary gland will have been removed with the integument; 

 it is lo be examined by removing the fascia and cellular tissue cover- 

 ig its base. The tubuli of the nipple may be demonstrated by the 

 insinuation of a bristle into their orifices. 



The MAMMARY GLAND rests upon the pectoralis major 

 luscle, and is separated from it only by a layer of fascia, 

 [n the male subject the gland is rudimentary; in the female 

 it varies in size and development. It consists of lobules 

 md lobes, from which issue lactiferous ducts, connected 

 )gether by fibrous and adipose tissue. The nipple is a 

 uiical prominence projecting from the centre of the gland, 

 at which open the tubuli galactophori, about twenty in 

 number, formed by the union- of the converging lactiferous 

 ducts. The nipple is surrounded by an areola or colored 

 ring, the shade of which is influenced by complexion, and 

 upon which numerous papillae will be noticed. 



The pectoralis major and the deltoid muscles are sepa- 

 rated from each other by a groove in which lies the cephalic 

 vein, ascending from the elbow, and an artery, the descend- 

 ing branch of the thoracica acromialis. 



The deltoid muscle covers the shoulder and cannot be exposed in 

 its totality until the subject be turned upon its face. It is composed 

 of coarse muscular bundles, difficult of dissection from the impossi- 

 bility of making them tense ; this is best effected by bringing the arm 

 down to the side and rotating it firmly inward. 



* 



The DELTOID MUSCLE arises from the external third of 

 the clavicle, from the lower border of the acromion process, 

 and from the inferior border of the spine of the scapula, as 

 far as the triangular space which terminates it, and is 

 inserted into the rough triangular eminence on the outer 

 aspect of the shaft of the humerus. The anterior fibres 

 cover the tendon of the pectoralis major and are in contact 

 with the upper part of the biceps ; posteriorly they are 

 bound down by fascia. This muscle covers the convex 

 head of the humerus and the insertions of the scapular 

 muscles into the tuberosities of that bone. A bursa, more 

 or less apparent, lies between these tendons and the under 

 surface of the deltoid muscle. 



9* 



